Two-stage coal liquefaction process with process-derived solvent having a low heptane-insolubles content

Abstract

Disclosed is a two-stage process for the production of clean liquid hydrocarbons from coal. In the process subdivided coal is dissolved in a process derived solvent. The dissolver effluent is passed through a catalytic reactor operating under hydrocracking conditions, to produce normally liquid products and recycle solvent. The solvent is further cooled to precipitate unconverted heptane-insolubles prior to recycle to the dissolution stage.

What is claimed is: 
     
       1. A process for liquefying coal which comprises: forming a coal-solvent slurry by mixing subdivided coal with a solvent; passing said slurry with added hydrogen through a dissolving zone to substantially dissolve said coal to produce a first effluent;   contacting at least a portion of said first effluent from said dissolving zone in a reaction zone containing hydrocracking catalyst under hydrocracking conditions to produce a second effluent, having a normally liquid portion containing heptane-insolubles;   cooling at least a portion of said normally liquid portion of said second effluent to precipitate substantially all of said heptane-insolubles; and   recycling at least a portion of the cooled, substantially heptane-insoluble-free, liquid portion for use as coal solvent.   
     
     
       2. A process as recited in claim 1, wherein said portion of said normally liquid portion of said second effluent is cooled to a temperature in the range 16° C.-95° C. 
     
     
       3. A process as recited in claim 1, wherein said portion of said normally liquid portion of said second effluent is a 200° C.+ boiling fraction. 
     
     
       4. A process as recited in claim 1, wherein the normally liquid portion of said second effluent containing heptane-insolubles has a heptane-insolubles content in the range of 2 to 5 weight percent. 
     
     
       5. A process as recited in claim 1 wherein precipitated heptane-insolubles are separated by filtration, gravity settling, hydrocloning, centrifugation or any combination of filtration, gravity settling, hydrocloning, and centrifugation. 
     
     
       6. A process as recited in claim 1 wherein precipitated heptane-insolubles are separated by filtration. 
     
     
       7. A process as recited in claim 1 wherein precipitated heptane-insolubles are separated by centrifugation. 
     
     
       8. A process as recited in claim 1 wherein precipitated heptane-insolubles are separated by hydrocloning. 
     
     
       9. A process as recited in claim 1 wherein precipitated heptane-insolubles are separated by gravity settling. 
     
     
       10. A process for liquefying coal which comprises: forming a coal-solvent slurry by mixing subdivided coal with a solvent;   passing said slurry with added hydrogen through a dissolving zone to substantially dissolve said coal to produce a first effluent;   contacting at least a portion of said first effluent from said dissolving zone in a reaction zone containing hydrocracking catalyst under hydrocracking conditions to produce a second effluent having a normally liquid portion which contains heptane-insolubles and coal residue;   separating a substantial portion of the coal residue from at least a portion of said normally liquid portion of said second effluent to produce a solids-lean liquid;   cooling at least a portion of said solids-lean liquid to precipitate substantially all of said heptane-insolubles; and   recycling at least a portion of the cooled, substantially heptane-insoluble-free liquid for use as a coal solvent.   
     
     
       11. A process as recited in claim 10, wherein said portion of said solids-lean liquid is cooled to a temperature in the range 16° C.-95° C. 
     
     
       12. A process as recited in claim 11, wherein said portion of the normally liquid portion of said second effluent is a 200° C.+ boiling fraction. 
     
     
       13. A process as recited in claim 11, wherein said normally liquid portion of said second effluent has a heptane-insolubles content in the range of 2 to 5 weight percent. 
     
     
       14. A process as recited in claim 10 wherein said portion of the coal residue is separated by hydrocloning, filtering, centrifuging, gravity settling, or any combination of hydrocloning, filtering, centrifuging, or gravity settling. 
     
     
       15. A process as recited in claim 10 wherein said portion of the coal residue is separated by hydrocloning. 
     
     
       16. A process as recited in claim 10 wherein said portion of the coal residue is separated by filtration. 
     
     
       17. A process as recited in claim 10 wherein said portion of the coal residue is separated by centrifuging. 
     
     
       18. A process as recited in claim 10 wherein said portion of the coal residue is separated by gravity settling. 
     
     
       19. A process as recited in claim 1 or 10 wherein the entire effluent from the dissolving zone is passed to the reaction zone containing hydrocracking catalyst. 
     
     
       20. A process as recited in claim 1 or 10 wherein water and light gases are removed from the effluent from the dissolving zone prior to passage of the remaining effluent to the reaction zone containing hydrocracking catalyst. 
     
     
       21. A process for liquefying coal which comprises: forming a coal-solvent slurry by mixing subdivided coal with a solvent;   passing said slurry with added hydrogen through a dissolving zone to substantially dissolve said coal to produce a first effluent;   contacting at least a portion of said first effluent from said dissolving zone in a reaction zone containing hydrocracking catalyst under hydrocracking conditions to produce a second effluent, having a normally liquid portion containing heptane-insolubles;   cooling at least a portion of said normally liquid portion of said second effluent to precipitate at least a substantial portion of the heptane-insolubles therein, thereby producing a hydrocarbon liquid having a substantially reduced heptane-insolubles content; and   recycling at least a portion of the cooled, hydrocarbon liquid having a substantially reduced heptane-insolubles content for use as coal solvent.   
     
     
       22. A process as recited in claim 21, wherein said portion of said normally liquid portion of said second effluent is cooled to a temperature in the range 16° C.-95° C. 
     
     
       23. A process as recited in claim 21, wherein said portion of said normally liquid portion of said second effluent is a 200° C.+ boiling fraction. 
     
     
       24. A process as recited in claim 21, wherein the normally liquid portion of said second effluent containing heptane-insolubles has a heptane-insolubles content in the range of 2 to 5 weight percent. 
     
     
       25. A process as recited in claim 21 wherein precipitated heptane-insolubles are separated by filtration, gravity settling, hydrocloning, centrifugation or any combination of filtration, gravity settling, hydrocloning, and centrifugation. 
     
     
       26. A process for liquefying coal which comprises: forming a coal-solvent slurry by mixing subdivided coal with a solvent;   passing said slurry with added hydrogen through a dissolving zone to substantially dissolve said coal to produce a first effluent;   contacting at least a portion of said first effluent from said dissolving zone in a reaction zone containing hydrocracking catalyst under hydrocracking conditions to produce a second effluent having a normally liquid portion which contains heptane-insolubles and coal residue;   separating a substantial portion of the coal residue from at least a portion of said normally liquid portion of said second effluent to produce a solids-lean liquid;   cooling at least a portion of said solids-lean liquid to precipitate at least a substantial portion of the heptane-insolubles therein, thereby producing a hydrocarbon liquid having a substantially reduced heptane-insolubles content; and   recycling at least a portion of the cooled hydrocarbon liquid having a substantially reduced heptane-insolubles content for use as coal solvent.   
     
     
       27. A process as recited in claim 26, wherein said portion of said solids-lean liquid is cooled to a temperature in the range 16° C.-95° C. 
     
     
       28. A process as recited in claim 27, wherein said portion of the normally liquid portion of said second effluent is a 200° C.+ boiling fraction. 
     
     
       29. A process as recited in claim 27, wherein said normally liquid portion of said second effluent has a heptane-insolubles content in the range of 2 to 5 weight percent. 
     
     
       30. A process as recited in claim 26 wherein said portion of the coal residue is separated by hydrocloning, filtering, centrifuging, gravity settling, or any combination of hydrocloning, filtering, centrifuging, or gravity settling. 
     
     
       31. A process as recited in claim 21 or 26 wherein the entire effluent from the dissolving zone is passed to the reaction zone containing hydrocracking catalyst. 
     
     
       32. A process as recited in claim 21 or 26 wherein water and light gases are removed from the effluent from the dissolving zone prior to passage of the remaining effluent to the reaction zone containing hydrocracking catalyst. 
     
     
       33. A process as recited in claims 21, 22, 24, 26, 27 or 29 wherein said hydrocarbon liquid having a reduced heptane-insolubles content contains less than one weight percent heptane-insolubles. 
     
     
       34. A process as recited in claims 21, 22, 24, 26, 27, or 29 wherein said hydrocarbon liquid having a reduced heptane-insolubles content contains less than 0.5 weight percent heptane-insolubles. 
     
     
       35. A process as recited in claim 21, 22, 24, 26, 27 or 29 wherein said hydrocracking conditions in said reaction zone include a temperature within the range of 340°-400° C. a pressure of 70 to 205 atmospheres, a hydrogen rate of 355 to 3550 liters per liter of slurry, and a slurry hourly space velocity in the range of 0.1-2. 
     
     
       36. A process as recited in claim 33 wherein said hydrocracking conditions in said reaction zone include a temperature within the range of 340°-400° C., a pressure of 70 to 205 atmospheres, a hydrogen rate of 355 to 3550 liters per liter of slurry, and a slurry hourly space velocity in the range of 0.1-2. 
     
     
       37. A process as recited in claim 34 wherein said hydrocracking conditions in said reaction zone include a temperature within the range of 340°-400° C., a pressure of 70 to 205 atmospheres, a hydrogen rate of 355 to 3550 liters per liter of slurry, and a slurry hourly space velocity in the range of 0.1-2.